To the Editor:

We read with great interest the article by Ferraro et al (July 2004)1assessing ventilation during elective endoscopic-guided percutaneous tracheostomy, and we have some questions and comments. We agree that bronchoscopic guidance has increased the safety of the procedure and may prevent complications.2–3 We do not agree, however, that the presence of the bronchoscope inside the lumen of the endotracheal tube and trachea produce clinically important airway obstruction leading to hypoventilation, hypercarbia, and hypoxemia.

First, the period during which the bronchoscope is present (ie, from the moment of puncture until dilatation), is relatively short, especially when the Ciaglia Blue Rhino technique is used (Cook; Son, the Netherlands). Indeed, Ferraro et al1 show that the duration of this procedure (from incision of the skin to insertion of the tracheostomy tube) is only 2.45 ± 1.36 min (mean ± SD). Keeping in mind that 1 min of this time period is used for the single one-step dilator to dilate the trachea wall, the time period during which the bronchoscope is present in the airways is even shorter.

Second, in our experience, hypoventilation during the procedure is only present during the short period of dilation of the trachea. To demonstrate this, we present end-tidal CO2 levels in five consecutive patients in our clinic. In these patients, we used the Ciaglia Blue Rhino technique. To assess ventilation during the procedure, we withdrew the endotracheal tube with the cuff just above the vocal cords; the cuff was then re-inflated. Tidal volumes were kept constant, and pressure limits were adjusted. For bronchoscopic guidance, we used a tracheal intubation fiberscope (Olympus LF-GP; Olympus Winter & Ibe; Hamburg, Germany). As can be seen in Figure 1
, during the 5 min when the scope was present in the airways (indicated by the arrow), there was no rise in end-tidal CO2 levels. Furthermore, even dilation does not result in a rise in end-tidal CO2 levels. Based on our experience, we prefer this technique above one in which a potential dangerous procedure must be performed (changing the endotracheal tube).

Figure Jump LinkFigure 1.End-tidal (etCO2) values in five consecutive patients during percutaneous dilational bronchoscopy. The separate phases of the procedure are indicated by arrows. Data are presented as mean ± SD.Grahic Jump Location

To the Editor:

We thank Dr. Dongelmans and his coworkers for their interest in our study (July 2004)1and for sharing their data. We agree that the use of a small-sized scope (⊘, < 4 mm) generally may allow adequate ventilation around the bronchoscope during a percutaneous tracheostomy, but these smaller scopes also do not permit secretions to be adequately cleared from view.2–3 Nevertheless, a separate operator is required to maintain the withdrawn endotracheal tube with the cuff just above the vocal cords, a very proximal scope position that provides little margin for safety against extubation.3–4 We proposed our procedure because changing the endotracheal tube is safe when using a tube exchanger, even in cases of difficult airways, and ensures airway control during the whole procedure.1

The following are not clear from the data reported by Dongelmans:

Which are the clinical and respiratory baseline characteristics of their five patients?

How do the end-tidal carbon dioxide concentration (Etco2) levels vary during the critical moments of the procedure, which begins with the maneuver of dilatation and ends with the tracheostomy tube placed? It is not clear whether the scope is disturbed during these two important phases. Also, a few minutes after the tracheostomy tube has been positioned, the registration of important and/or dangerous variations of the Etco2 could be missing.5

How much were the pressure limits adjusted?

How were the tidal volumes maintained at a constant flow during tracheal obstruction by the dilator?

In our study of 40 patients, the technique used ensured airway control with continuous pressure control ventilation, thanks to the gas supply at the carina level, so that it did not interfere with the surgical field and when the operating time was unexpectedly prolonged. Also, it allows the use of a normal flexible fiberoptic bronchoscope (⊘, 6 mm) for the whole procedure, without interfering with ventilation. The ventilation technique that we proposed seems to be secure independently from the percutaneous procedure used in stabilized critically ill patients (mean [± SD] APACHE [acute physiology and chronic health evaluation] III score, 56.80 ± 24.03; Pao2/fraction of inspired oxygen ratio, 253.41 ± 94.83), in whom even a short apnea time can be dangerous.

Return to: Assessment of Ventilation During the Performance of Elective Endoscopic-Guided Percutaneous Tracheostomy

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